ISSN:0022-104X    

DOI:10.1002/jez.1401900202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractIn absence of the anterior pituitary gland, limb and tail regeneration does not occur in the adult newtNotophthalmus (Diemictylus) viridescens. Sixty‐five adult newts were included in this work which was designed to test to what degree a hypophysectomized newt can regenerate its forelimb when given daily injections of fresh adult or stored (−20° C)‐thawed embryonic or adult chicken anterior pituitary gland extract. Injections were begun seven days after hypophysectomy (to minimize further the titres of residual circulatory hormones) and concomitant amputation. The results are based on three experimental, one control and one sham series.In 40 out of 45 cases in Experiments C, D, and E, limb regeneration ensued for 25–30 days post‐amputation (until fixation). However, in the Experiment E newts, which were given embryonic chick pituitary extract, the regenerates were less advanced than those seen in the animals of Experiments C and D, given adult chicken pituitary extracts. Possible explanations for the differences in results are discussed.The results show that forelimb regeneration and survival in our hypophysectomized animals were due to extracts of embryonic or adult chicken anterior pituitary glands; presumably, these extracts contained the essential hormones. On the basis of our newt bio‐test system, 15–18 day chick embryo and adult chicken anterior pituitary extracts (hormones) are not species specific. Freezing and storage of extracts at −20° C for up to three months before thawing and use apparently does not appreciably affect their

ISSN:0022-104X    

DOI:10.1002/jez.1401900203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractPreparations of ungulate growth hormone that have been used thus far to establish the role of that compound in supporting limb regeneration in hypophysectomized newts have contained significant prolactin contamination. Prolactin when present with thyroxin has been shown to be effective at low doses in supporting limb regeneration in these animals. The present communication demonstrates that a highly purified preparation of bovine growth hormone is able to support limb regeneration in hypophysectomized newts at essentially normal levels. Previous results indicating that prolactin and thyroxin in combination restore the regenerative response are corroborated. Thyroxin alone, or prolactin alone, gave a much reduced response. Purified growth hormone, while effective alone, is apparently antagonized by the presence of thyroxin.

ISSN:0022-104X    

DOI:10.1002/jez.1401900204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractA study, mainly by electron microscopy, has been made on the forelimb musculature ofAmbystoma opacumlarvae following removal of the presumptive limb innervation in the embryo. In the aneurogenic limbs, early development and differentiation of striated muscle occurs at the same rate as in normal animals. At the time of nerve ingrowth into the normal limb, both myotubes and differentiated myofibers of small diameter are present. With the failure to make contact with nerves, the aneurogenic muscle does not advance beyond the early myofiber stage and soon (1–2 weeks) begins to show signs of atrophy. As has been described in studies of denervated adult muscle, the breakdown seems to be in two phases overlapping in time. In the first, a degenerative autolysis takes place, leading to loss of striation. There is dissolution of the Z bands, followed by disorder of the myofilaments. During this process there is evidence of fragmentation of the muscle fiber, both into nucleated and anucleate portions; waste sarcoplasm is thought to be discarded into the intercellular spaces. Interestingly enough, with the techniques used, no sign of lysosomes was noted and only a few macrophages were seen. The second phase of muscle breakdown is one with characteristics of atrophy, where single myofibers undergo gradual reduction in diameter. This process seems to take place by detachment of filaments from the periphery of the fibers and by their subsequent breakdown in the interfibrillary spaces. Late stages of muscle deterioration show large areas of cytoplasm containing scattered ribosomes, small vesicles, and a few mitochondria. The final picture is of densely stained irregular nuclei surrounded by a thin rim of cytoplasm; the intercellular spaces contain a considerable amount of fibrous material. The cartilage and skin of the aneurogenic limb appear normal even after the latest stages of muscle deterioratio

ISSN:0022-104X    

DOI:10.1002/jez.1401900205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractFrogs and tadpoles (Rana pipiens) were treated with mammalian prolactin or growth hormone for several days, then injected with14C‐leucine. Fourteen to sixteen hours later the animals were killed and the amount of label incorporated into protein of muscle, liver, and gut was measured.Growth hormone stimulated the incorporation of leucine into protein of gastroenemius muscle and small intestine, but not liver, of the frog. Prolactin had no effect on amino acid incorporation in any of these tissues in the frog. Prolactin stimulated the incorporation of leucine into protein of tail muscle, intestine and liver of tadpoles. The effect was not entirely consistent, and was of a smaller magnitude than was expected on the basis of the growth‐promoting effects of prolactin in tadpoles. This problem is discussed. Growth hormone had no effect on protein synthesis in any of these tissues in any experim

ISSN:0022-104X    

DOI:10.1002/jez.1401900206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractBlood glucose inAmbystoma tigrinumis regulated at a lower level in larval (18.4 ± 0.7 mg%) than in adult (27.8 ± 0.8 mg%) animals. The difference is observed at all seasons, and is not related to differences in size, diet or sexual maturity. A difference in the blood glucose regulating mechanism in pre‐ and post‐metamorphic animals is further shown by three other observations: (1) larvae are more insulin sensitive than adults; (2) larvae have a slightly greater glucose tolerance than adults; and (3) pancreatectomy causes a more severe hyperglycemia in adults than in larvae.The best hypothesis to account for all of these observations is that an increase in the amount and/or activity of insulin antagonistic hormones occurs at metamorp

ISSN:0022-104X    

DOI:10.1002/jez.1401900207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractThe regenerating and stump tissues of amputated forelimbs of the adult newt,Diemictylus viridescens, were analyzed for collagen content and synthesis. Collagen soluble and insoluble in 0.45MNaCl was assayed by (1) spectrophotometric determination of hydroxyproline, (2) radiotracer determination of14C‐proline incorporation, and (3) radiochromatographic analysis of the14C‐proline/14C‐hydroxyproline ratio in the two collagen fractions.The results obtained reveal that there is significantly less saline insoluble as well as soluble collagen in the regenerating limb tissues than in the basal stump of the amputee, though a soluble fraction is demonstrable throughout the course of regeneration. By ninety days after amputation, there is a significant increase in the insoluble collagen fraction in the regenerating limb.The soluble collagen fractions assayed in the regenerating tissues are newly synthesized protein, and this synthetic activity appears to be greatest during the paddle and early digitiform stages of regeneration. The soluble collagen extracted from regenerates appears to be less completely hydroxylated with respect to hydroxyproline content than obtains in corresponding fractions from limb stump and control limb ti

ISSN:0022-104X    

DOI:10.1002/jez.1401900208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractRegenerating and non‐regenerating limb tissues from the adult newt,Diemictylus viridescens, were assayed for isocitrate lyase activity. The enzyme assays were performed by micromodifications of existing procedures. In general, the whole homogenate, or a soluble fraction of the homogenate, was incubated with the substrate isocitrate. Isocitrate is cleaved by isocitrate lyase to glyoxylate and succinate. At the termination of the reaction, the 2,4‐dinitrophenylhydrazone derivative of glyoxylate was produced, extracted and quantitated spectrophotometrically. Isocitrate lyase activity was localized to bulb and two‐digit regenerates. The reaction product, glyoxylate (a monocarboxylic keto acid), was of special interest due to its role as a potent in vitro metabolic inhibitor. Therefore, the endogenous level of monocarboxylic keto acids, and the ability of regenerating tissue to produce and accumulate monocarboxylic keto acids, were investigated. Whole homogenates of regenerating tissue always contained more monocarboxylic keto acids than intact forearm or stump tissue. Also, after 30 minutes incubation with buffer alone, only regenerating tissue produced and accumulated additional monocarboxylic keto acids. In regenerating tissue, the isocitrate lyase reaction may be utilized in the metabolism of lipid. Since regenerating tissue can produce and accumulate monocarboxylic keto acids in vitro, glyoxylate produced by the isocitrate lyase reaction may accumulate in vivo and participate in metabolic regul

ISSN:0022-104X    

DOI:10.1002/jez.1401900209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractDuring the process of amphibian limb regeneration muscle fibers injured by the amputation lose their myofibrils and sarcoplasmic systems of membrane. Fragmentation of many of these dedifferentiated fibers to produce regeneration blastema cells has been reported numerous times by other investigators. The present work utilizing the electron microscope calls attention to dedifferentiated fibers that contain numerous helical polyribosomes and disorganized myofilaments. A number of polysome‐filled cells can be found beside mature muscle fibers as if in the process of fusing. In embryonic muscle, individual myoblasts containing helical polysomes fuse continually to form multinucleated fibers. The presence of the helical polysomes and myofilaments in sparsely fibrillar muscle elements of the regenerating limb, together with other features, is taken as evidence that the muscle elements are stages of regenerating fibers. These regenerating fibers can be found several days before the blastema becomes visible at the limb tip and are a normal part of the overall regeneration process. Indeed, tissue regenerative events marked by the appearance of helical polysomes become evident so soon after muscle injury/amputation that they imply a continuous but probably subliminal tissue turnover that is unmasked by the injury. According to the degree of injury, either the synthetic or the destructive phase of turnover might be favored, resulting in repair or extensive dedifferentiation of the individual fibers. Whether tissue regeneration or blastema cell formation thereafter occurs seems to be determined in part by the closeness of the fibers to the amputation surfac

ISSN:0022-104X    

DOI:10.1002/jez.1401900210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY

摘要:

AbstractThe effect of hydrocortisone on the anti‐erythrocyte (SRBC) response of the South African clawed toad,Xenopus laevis, was studied. Hydrocortisone was administered two days prior to antigen injection and was found to reduce the eight‐day antigen‐binding response of sensitized spleen cells to 17% of its normal peak value. Control animals received injections of the vehicle solution the hormone is normally suspended in. Hemagglutination assays were also performed to ascertain whether the hydrocortisone treatment merely altered the ability of the spleen cells to bind antigen or suppressed their ability to produce antibody. Serum antibody titers were found to be depressed to 9% of the peak value by hydrocortisone treatment. Both thymus and spleen cells from the sensitized, hydrocortisone‐treated and control adultXenopuswere tested by immunocytoadherence. Unimmunized animals were also used to establish background levels. It was found that while the antigen‐binding response by immunized spleen cells was greatly decreased by hydrocortisone, thymocytes were particularly effected as their antigen‐binding capacities were reduced to background levels. It was concluded that these data support the view that the toad immune system is comparable to the mammalian with regard to hydrocortisone sensitivity of the anti‐red

ISSN:0022-104X    

DOI:10.1002/jez.1401900211

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1974

数据来源: WILEY